Device for the pressure fixing of toners

Abstract

A device for the pressure fixing of a toner on a record carrier under ambient temperatures has a stand; a first pressure roll of relatively large diameter rotatably and stationarily supported in the stand; and a second pressure roll of relatively small diameter rotatably supported in the stand and cooperating with the first pressure roll to define therewith a roll gap. The second pressure roll is displaceably supported to be shiftable towards and away from the roll gap. The device further has a plurality of pressure rollers arranged in a series along the length dimension of the second pressure roll in an axially parallel orientation therewith and a support for individually displaceably supporting each pressure roller for movement towards and away from the roll gap. A separate spring urges each pressure roller into contact with the second pressure roll for exerting thereon a pressing force with which the first and second rolls compress a record carrier passing through the roll gap. With each pressure roller there is associated a setting mechanism for individually adjusting the pressing force exerted by each pressure roller.

What is claimed is: 
     
       1. In a device for the pressure fixing of a toner on a record carrier under ambient temperatures; the device including a stand; a first pressure roll of relatively large diameter rotatably and stationarily supported in the stand; a second pressure roll of relatively small diameter rotatably supported in the stand and cooperating with the first pressure roll to define therewith a roll gap; means for displaceably supporting the second pressure roll to be shiftable towards and away from the roll gap; resilient force-exerting means for urging the second pressure roll against the first pressure roll; the improvement wherein said resilient force-exerting means comprises (a) a plurality of pressure rollers arranged in a series along the length dimension of said second pressure roll; said pressure rollers being oriented axially parallel with said second pressure roll;   (b) a separate support means for individually displaceably supporting each said pressure roller for movement towards and away from said roll gap;   (c) a separate spring urging each said pressure roller into contact with said second pressure roll for exerting thereon a pressing force with which said first and second rolls compress a record carrier passing through said roll gap; and   (d) setting means for individually adjusting the pressing force exerted by each said pressure roller.   
     
     
       2. A device as defined in claim 1, wherein each said separate support means comprises a lever pivotally supported in the stand; said lever formed of first and second lever arms; said first lever arm rotatably carrying the pressure roller and said second lever arm being in engagement with said separate spring; said setting means comprising a set screw threadedly held in a stationary component adjacent said second lever arm; said set screw being in engagement with said spring for adjusting the bias thereof upon turning said set screw in the stationary component. 
     
     
       3. A device as defined in claim 2, wherein said second lever arm includes a saddle portion oriented perpendicularly to the pivotal direction of the lever; said saddle portion being provided with an aperture through which said set screw passes; said set screw having a head; said spring being arranged for compression between the screw head and said saddle portion. 
     
     
       4. A device as defined in claim 1, wherein said first and second pressure rolls are metal rolls with a hard surface; at least one of said pressure rolls having a smooth surface for contacting the image-carrying surface of the record carrier upon its passage through said roll gap. 
     
     
       5. A device as defined in claim 1, wherein said second pressure roll is arranged underneath said first pressure roll and said pressure rollers are arranged underneath said second pressure roll; said second pressure roll engaging, at least by its own weight, said pressure rollers for displacing the same to define an air gap between said first and second pressure rolls; the improvement further comprising limiting means for setting the magnitude of said air gap; said air gap being smaller than the thickness of the record carrier. 
     
     
       6. A device as defined in claim 2, wherein said second pressure roll is arranged underneath said first pressure roll and said pressure rollers are arranged underneath said second pressure roll; said second pressure roll engaging, at least by its own weight, said pressure rollers for displacing the same to define an air gap between said first and second pressure rolls; the improvement further comprising limiting means for setting the magnitude of said air gap; said limiting means including a separate adjustable abutment associated with each said lever and supported in said stand; said separate adjustable abutment being engaged by the respective lever in the absence of a record carrier between said first and second pressure rolls; said separate adjustable abutment setting the air gap to a magnitude that is smaller than the thickness of the record carrier. 
     
     
       7. A device as defined in claim 6, wherein said adjustable abutment comprises a screw threadedly held in said stand. 
     
     
       8. A device as defined in claim 6, wherein said separate adjustable abutment is formed of a cam disc.